Reciprocating saw

ABSTRACT

A power tool includes a housing, a motor, and a drive mechanism. The drive mechanism includes a driven gear that is rotated by the motor. The driven gear is vertically-oriented within the housing and has an upper portion and a lower portion. The drive mechanism also includes a connecting rod coupled to the driven gear to translate rotary motion of the driven gear into reciprocating motion, and an output shaft coupled to the connecting rod to reciprocate relative to the housing through a cutting stroke and a return stroke. The drive mechanism further includes a counterweight coupled to the driven gear for rotation with the driven gear. The counterweight moves through the upper portion of the driven gear during the cutting stroke of the output shaft, and moves through the lower portion of the driven gear during a return stroke of the output shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/296,892, filed Jun. 5, 2014, which is a continuation-in-part of U.S.patent application Ser. No. 12/842,209, filed Jul. 23, 2010, and claimspriority to U.S. Provisional Patent Application No. 61/831,968, filedJun. 6, 2013, the entire contents of all of which are incorporated byreference herein.

BACKGROUND

The present invention relates to power tools and, more particularly, toreciprocating saws.

Power tools include different types of drive mechanisms to perform work.Power tools with reciprocating-type drive mechanisms commonly includecounterweights to counterbalance forces generated by output elements(e.g., saw blades) during reciprocating movement. Due to the orientationof the counterweights within the power tools, however, movement of thecounterweights may generate inertia that tends to move the power toolsaway from work pieces while the power tools are operating.

SUMMARY

In one embodiment, the invention provides a power tool including ahousing and a motor positioned within the housing. The motor includes apinion. The power tool also includes a drive mechanism positioned withinthe housing and coupled to the motor. The drive mechanism includes adriven gear that engages the pinion and is rotated by the motor. Thedriven gear is vertically-oriented within the housing and has an upperportion and a lower portion. The drive mechanism also includes aconnecting rod coupled to the driven gear to translate rotary motion ofthe driven gear into reciprocating motion, and an output shaft coupledto the connecting rod to reciprocate relative to the housing through acutting stroke and a return stroke. The output shaft is configured tosupport a tool element. The drive mechanism further includes acounterweight coupled to the driven gear for rotation with the drivengear. The counterweight moves through the upper portion of the drivengear during the cutting stroke of the output shaft, and moves throughthe lower portion of the driven gear during a return stroke of theoutput shaft.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a reciprocating saw embodying theinvention.

FIG. 2 is a side view of the reciprocating saw with a portion of ahousing removed.

FIG. 3 is a top view of the reciprocating saw with a portion of thehousing removed.

FIG. 4 illustrates a saw blade for use with the reciprocating saw.

FIG. 5 is a graph depicting vertical vibration caused by a counterweightmoving in accordance with the present invention.

FIG. 6 is a graph depicting vertical vibration caused by a counterweightmoving in an opposite direction than the present invention.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

DETAILED DESCRIPTION

FIGS. 1-3 illustrate a power tool 10. In the illustrated embodiment, thepower tool 10 is a reciprocating saw. In other embodiments, the powertool 10 may be another type of device that utilizes a reciprocating-typedrive mechanism, such as a jigsaw, a sabre saw, a hammer drill, or thelike.

The illustrated reciprocating saw 10 includes a housing 14, a motor 18positioned within the housing 14, and a drive mechanism 22 coupled tothe motor 18 and positioned within the housing 14. As shown in FIG. 1,the housing 14 is comprised of two clamshell halves 24A, 24B that areconnected together along a plane 25 (FIG. 3). In the illustratedembodiment, the clamshell halves 24A, 24B are secured together withthreaded fasteners (e.g., screws), but may alternatively be securedtogether using other suitable coupling means. FIG. 2 illustrates thereciprocating saw 10 with one of the clamshell halves 24A removed tofacilitate illustration of the internal components (e.g., the motor 18,the drive mechanism 22, etc.) of the saw 10.

Referring back to FIG. 1, the housing 14 includes a rearward portion 26,a forward portion 30, and a battery support portion 34. The housing 14also defines a longitudinal axis 38 (FIG. 2) that extends through therearward and forward portions 26, 30. The rearward portion 26 includes aD-shaped handle 42, and the forward portion 30 includes a grip 46. TheD-shaped handle 42 and the grip 46 are configured to be grasped by auser during operation of the reciprocating saw 10. An actuator ortrigger 50 is supported by the rearward portion 26 adjacent the D-shapedhandle 42. The trigger 50 is actuatable by a user to selectively powerthe motor 18. In the illustrated embodiment, the trigger 50 ispositioned above the longitudinal axis 38, and the longitudinal axis 14generally divides the housing 14 into an upper section and a lowersection. A shoe 54 extends from and is pivotally coupled the forwardportion 30 of the housing 14. The shoe 54 pivots about a pivot axis 56and facilitates aligning the reciprocating saw 10 on a work piece to becut.

The battery support portion 34 is formed on the rearward portion 26 ofthe housing 14 below the D-shaped handle 42. In the illustratedembodiment, the battery support portion 34 is located beneath thelongitudinal axis 38 of the housing 14 when the reciprocating saw 10 isviewed as shown in FIG. 2. In other embodiments, the battery supportportion 34 may be located elsewhere on the housing 14. The batterysupport portion 34 is configured to receive a battery pack (e.g., an 18volt Li-ion power tool battery pack) and electrically connect thebattery pack to the motor 18. In other embodiments, the battery pack mayhave different voltages and/or chemistries. In still other embodiments,the reciprocating saw 10 may include a power cord such that the motor 18is powered by an AC power source (e.g., a wall outlet, a portablegenerator, etc.).

As shown in FIG. 2, the motor 18 is positioned within the housing 14between the rearward portion 26 and the forward portion 30. The motor 18is also electrically connected to the battery pack (or other suitablepower source) through the trigger 50. As shown in FIG. 3, the motor 18includes a motor shaft 58 and an output gear or pinion 62. Referringback to FIG. 2, the motor shaft 58 defines a central longitudinal axis70, or motor axis, of the motor 18. In the illustrated embodiment, thecentral longitudinal axis 70 of the motor 18 is generally aligned orcoaxial with the longitudinal axis 38 of the housing 14. When powered,the motor 18 rotates the motor shaft 58 and the pinion 62 about the axis70 to drive the drive mechanism 22.

As shown in FIGS. 2 and 3, the drive mechanism 22 is positioned at leastpartially within the forward portion 30 of the housing 14 between themotor 18 and the shoe 54. The illustrated drive mechanism 22 is aslider-crank mechanism that includes a driven gear 74, a connecting rod78, and an output shaft 82. However, other mechanisms known in the art,such as a scotch-yoke mechanism, are also contemplated. The driven gear74 engages the pinion 62 of the motor 18 and defines a central axis 86about which the gear 74 rotates. In the illustrated embodiment, thecentral axis 86 is perpendicular to the longitudinal axis 38 of thehousing 14, extends between opposing sides of the housing 14, and isparallel to the pivot axis 56 of the shoe 54. More particularly, thecentral axis 86 is perpendicular to the plane 25 along which theclamshell halves 24A, 24B of the housing 14 are connected. The drivengear 74 is thereby vertically-oriented within the housing 14.

The longitudinal axis 38 of the housing 14 and the central axis 70 ofthe motor 18 extend through a center of the gear 74 (i.e., through thecentral axis 86) to divide the gear 74 into a first, or upper, portion90 and a second, or lower, portion 94. In the illustrated embodiment,the upper portion 90 of the driven gear 74 is located on the same sideof the longitudinal axis 38 as the output shaft 82 and the trigger 50,while the lower portion 94 of the driven gear 74 is located on the sameside of the longitudinal axis 38 as the battery support portion 34. Inother embodiments, the output shaft 82 may be located on the oppositeside of the longitudinal axis 38 such that the lower portion 94 of thedriven gear 74 is located on the same side of the longitudinal axis 38as the output shaft 38. It should be understand that what constitutesthe upper and lower portions 90, 94 of the driven gear 74 changes duringoperation of the drive mechanism 22 because the gear 74 rotates. Theterms “upper” and “lower” are simply illustrative terms used to helpdescribe volumes of spaces above and below the axes 38, 70 that areoccupied by sections of the gear 74 at any given time. At a particularinstance in time, the actual section of the gear 74 that qualifies asthe “upper portion” or the “lower portion” is different than at anotherinstance in time.

The connecting rod 78, or drive arm, includes a first end that iscoupled to the driven gear 74 by a crank pin 98 and a second end that iscoupled to the output shaft 82 by a pivot pin 102. The crank pin 98 isoffset from the central axis 86 of the driven gear 74 such that, as thegear 74 is rotated, the crank pin 98 moves about the central axis 86. Asthe first end of the connecting rod 78 moves with the driven gear 74,the second end of the connecting rod 78 pushes and pulls the outputshaft 82 in a reciprocating motion. The crank pin 98 allows theconnecting rod 78 to pivot vertically relative to the driven gear 74,while the pivot pin 102 allows the connecting rod 78 to pivot verticallyrelative to the output shaft 82.

The output shaft 82, or spindle, reciprocates within the forward portion30 of the housing 14 generally along a spindle axis 106. In theillustrated embodiment, the spindle axis 106 is generally parallel toand positioned above the longitudinal axis 38 of the housing 14. Rotarymotion of the motor 18 is thereby translated into linear reciprocatingmotion of the output shaft 82 by the driven gear 74 and the connectingrod 78.

The motor axis 70 and the spindle axis 106 together define a plane. Thedriven gear 74 is vertically-oriented within the housing 14 in that thegear 74 rotates about an axis (i.e., the central axis 86) that isperpendicular to the plane defined by the motor and spindle axes 70,106. In the illustrated embodiment, the plane defined by the motor andspindle axis 70, 106 is the same as the plane 25 (FIG. 3) along whichthe clamshell halves 24A, 24B are coupled together. In otherembodiments, one or both of the motor and spindle axes 70, 106 may beoffset from, yet still parallel to the plane 25.

With continued reference to FIG. 2, a blade clamp 110 is coupled to anend of the output shaft 82 opposite from the connecting rod 78. Theblade clamp 110 receives and secures a saw blade 112 (FIG. 4), or othertool element, to the output shaft 82 for reciprocating movement with theoutput shaft 82. The output shaft 82 supports the saw blade 112 suchthat, during operation of the reciprocating saw 10, the drive mechanism22 moves the saw blade 112 through a cutting stroke when the outputshaft 82 is pulled by the connecting rod 78 from an extended position toa retracted position, and through a return stoke when the output shaft82 is pushed by the connecting rod 78 from the retracted position to theextended position.

The illustrated drive mechanism 22 also includes a counterweight 114.The counterweight 114 helps balance forces generated by the output shaft82 and an attached saw blade during reciprocating movement. In theillustrated embodiment, the counterweight 114 and the driven gear 74 areseparate elements, but may alternatively be integrally formed as asingle piece. The illustrated counterweight 114 includes a connectionportion 118 and a mass portion 122. The connection portion 118 iscoupled to the connecting rod 78 via the crank pin 98. A guide pin 126also extends from the connection portion 118 and engages an innersurface of the housing 14. The guide pin 126 supports the counterweight114 within the housing 14 and defines an axis of rotation 130 of thecounterweight 114. In the illustrated embodiment, the axis of rotation130 of the counterweight 114 and the central axis 86 of the driven gear74 are generally coaxial so that the counterweight 114 and the drivengear 74 rotate about the same axis. Similar to the driven gear 74, thecounterweight 114 is, therefore, also vertically-oriented within thehousing 14. In the illustrated embodiment, the axis of rotation 130intersects and is perpendicular to the motor axis 70.

The mass portion 122 extends from the connection portion 118 andincludes a majority of the mass of the counterweight 114. As such,movement of the mass portion 122 in a direction opposite the movement ofthe output shaft 82 tends to balance the forces generated duringreciprocation of the saw blade in a front-to-back direction. In theillustrated embodiment, the mass portion 122 has a generallysemi-circular shape to match the circular shape and contour of thedriven gear 74. That is, the counterweight 114 is shaped and sized so itdoes not extend outside of (or only extends outside a minimal amount of)a vertical footprint area defined by the driven gear 74. Such anarrangement reduces the amount of space required within the housing 14to accommodate the counterweight 114. In other embodiments, the massportion 122 may have other suitable shapes or configurations.

As the driven gear 74 rotates and drives the crank pin 98, the massportion 122 of the counterweight 114 is moved in a substantiallyopposite direction than the output shaft 82 to counterbalance theinertial forces of the output shaft 82 and attached saw blade. Inparticular, the mass portion 122 of the counterweight 114 is in a firstposition (e.g., relatively close to the motor 18 and relatively far fromthe output shaft 82), as shown in FIG. 2, when the output shaft 82 is inthe extended position. The mass portion 122 of the counterweight 114rotates to a second position (e.g., relatively close to the output shaft82 and relatively far from the motor 18) when the output shaft 82 is inthe retracted position.

In the illustrated embodiment, the counterweight 114 rotates along apath P in a clockwise direction R (when viewing the reciprocating saw 10as shown in FIG. 2) about the axis of rotation 130 between the first andsecond positions. That is, the mass portion 122 of the counterweight 114travels generally above the longitudinal axis 38 of the housing 14 andthrough the upper portion 90 of the driven gear 74 during the cuttingstroke of the output shaft 82 to move from the first position to thesecond position. Conversely, the mass portion 122 of the counterweight114 travels generally below the longitudinal axis 38 of the housing 14and through the lower portion 94 of the driven gear 74 during the returnstroke of the output shaft 82 to move from the second position to thefirst position. Stated another way, as the mass portion 122 of thecounterweight 114 moves through a rearward half of the path P (i.e., thehalf of the path P that is closer to the rearward portion 26 of thehousing 14) at the end of the return stroke and start of the cuttingstroke, the mass portion 122 generally moves in an upward direction (asviewed in FIG. 2) and toward the spindle axis 106. As the mass portion122 of the counterweight 114 moves through a forward half of the path P(i.e., the half of the path P that is closer to the forward portion 30of the housing 14) at the end of the cutting stroke and start of thereturn stroke, the mass portion 122 generally moves in a downwarddirection (as viewed in FIG. 2) and away from the spindle axis 106. Thismovement of the counterweight 114 causes the front of the saw 10 to tendto move into a work piece (downward in FIG. 2) as the cutting strokebegins.

Because the counterweight 114 is coupled to the driven gear 74 by thecrank pin 98, the counterweight 114 does not actually move relative tothe gear 74. Instead, the counterweight 114 and the driven gear 74rotate together through the path P. As discussed above, the terms “upperportion” and “lower portion” of the driven gear 74 refer to volumes ofspace occupied by sections of the gear 74 during operation of the drivemechanism 22.

The arrangement of the counterweight 114 and the driven gear 74increases cutting performance of the reciprocating saw 10 compared withrotation of the counterweight 114 in the opposite direction (e.g.,counterclockwise when viewing the reciprocating saw 10 as shown in FIG.2). In particular, the mass portion 122 of the counterweight 114 tendsto move the saw 10 in the cutting direction during the non-cuttingstroke, which helps drive the reciprocating saw 10 and the saw blade 112into the work piece at the start of the next cutting stroke. Incontrast, if the counterweight 114 rotated in the opposite direction,the reciprocating saw 10 and the saw blade 112 may tend to move awayfrom the work piece during the start of the next cutting stroke. Byrotating the counterweight 114 in the clockwise direction R, a user canmore easily initiate cuts into a work piece and significantly reduce theamount of time required to cut through the work piece.

FIG. 5 is a graph depicting vibrations generated by the reciprocatingsaw 10 in a vertical direction during operation, while FIG. 6 is a graphdepicting vibrations generated by a reciprocating saw including acounterweight that is rotated in an opposite direction than thecounterweight 114 discussed above. As shown in FIG. 5, the velocity ofthe saw 10 lags its acceleration. Thus, the velocity of theclockwise-rotating saw 10 counterweight 114 is downward at the end ofthe return stroke and at the beginning of the cutting stroke. Thisdownward velocity results in a force that drives the saw 10, and moreparticularly the saw blade 112, into a work piece to start cutting thework piece. In contrast, the velocity of a counterclockwise-rotating saw10, as depicted in FIG. 6, results in a force that drives the saw 10 andthe saw blade 112 upward at the end of the return stroke and at thebeginning of the cutting stroke. With the arrangement depicted in FIG.6, the saw and saw blade are pulled away from a work piece at the startof each cut, which may cause the saw to “jump” and reduce cuttingefficiency.

Although the invention has been described with reference to certainpreferred embodiments, variations and modifications exist within thescope and spirit of one or more independent aspects of the invention.Various features and advantages of the invention are set forth in thefollowing claims.

The invention claimed is:
 1. A reciprocating saw comprising: a housing; a motor positioned within the housing, the motor including a pinion rotatable about a motor axis; and a drive mechanism positioned within the housing and coupled to the motor, the drive mechanism including a driven gear that engages the pinion and is rotated by the motor, the driven gear having a circumference and being vertically-oriented within the housing with the motor axis extending through a center of the driven gear to divide the driven gear into an upper portion and a lower portion, a connecting rod coupled to the driven gear to translate rotary motion of the driven gear into reciprocating motion, an output shaft coupled to the connecting rod to reciprocate relative to the housing through a cutting stroke and a return stroke, the output shaft configured to support a tool element, and a counterweight coupled to the driven gear and rotating with the driven gear through a path and in a same rotational direction, the counterweight moving through the upper portion of the driven gear during the cutting stroke of the output shaft, and moving through the lower portion of the driven gear during the return stroke of the output shaft, the counterweight including a connection portion coupled to the connecting rod and a mass portion including a leading edge, a trailing edge, and a curved outer perimeter matching the circumference of the driven gear, the curved outer perimeter extending more than 90 degrees between the leading and trailing edges.
 2. The reciprocating saw of claim 1, wherein the driven gear is rotated by the motor in the rotational direction about a central axis that is perpendicular to the motor axis.
 3. The reciprocating saw of claim 2, wherein the output shaft reciprocates along a spindle axis, and wherein the motor axis and the spindle axis define a plane, and wherein the driven gear rotates about the central axis perpendicular to the plane.
 4. The reciprocating saw of claim 3, wherein the central axis intersects the motor axis.
 5. The reciprocating saw of claim 3, wherein the spindle axis is generally parallel to the motor axis.
 6. The reciprocating saw of claim 1, wherein the mass portion includes an aperture positioned closer to the trailing edge than to the leading edge in the rotational direction.
 7. The reciprocating saw of claim 1, wherein the pinion is positioned between the driven gear and the counterweight.
 8. The reciprocating saw of claim 1, wherein as the counterweight moves through a rearward half of the path, the counterweight generally moves in an upward direction, and as the counterweight moves through a forward half of the path, the counterweight generally moves in a downward direction.
 9. The reciprocating saw of claim 1, wherein the housing includes a battery support portion and a handle, wherein the handle supports a trigger, and wherein the battery support portion and the trigger are located on opposite sides of the motor axis.
 10. A reciprocating saw comprising: a housing including a battery support portion; a motor positioned within the housing, the motor including a pinion rotatable about a motor axis; and a drive mechanism positioned within the housing and coupled to the motor, the drive mechanism including: a driven gear that engages the pinion and is rotated by the motor, the motor axis extending through a center of the driven gear to divide the driven gear into an upper portion and a lower portion, an output shaft driven by the motor to reciprocate relative to the housing through a cutting stroke and a return stroke, the output shaft being located on a same side of the motor axis as the upper portion of the driven gear and configured to support a tool element, and a counterweight coupled to the driven gear and rotating with the driven gear through a path and in a same rotational direction, the counterweight moving through the upper portion of the driven gear during the cutting stroke of the output shaft, and moving through the lower portion of the driven gear during the return stroke of the output shaft, wherein the battery support portion is positioned on a same side of the motor axis as the lower portion of the driven gear.
 11. The reciprocating saw of claim 10, wherein the driven gear is rotated by the motor in the rotational direction about a central axis that is perpendicular to the motor axis.
 12. The reciprocating saw of claim 11, wherein the output shaft reciprocates along a spindle axis, and wherein the motor axis and the spindle axis define a plane, and wherein the driven gear rotates about the central axis perpendicular to the plane.
 13. The reciprocating saw of claim 12, wherein the central axis intersects the motor axis.
 14. The reciprocating saw of claim 12, wherein the spindle axis is generally parallel to the motor axis.
 15. The reciprocating saw of claim 10, wherein the mass portion includes a leading edge, a trailing edge opposite the leading edge, and an aperture positioned closer to the trailing edge than to the leading edge in the rotational direction.
 16. The reciprocating saw of claim 10, wherein the pinion is positioned between the driven gear and the counterweight.
 17. The reciprocating saw of claim 10, wherein as the counterweight moves through a rearward half of the path, the counterweight generally moves in an upward direction, and as the counterweight moves through a forward half of the path, the counterweight generally moves in a downward direction. 